3 Answers
3

Box2D is very popular and well documented with lots of examples. Of course it's a full on physics library so it'll give you a good amount of flexibility for expanding later if you want. But you don't need to use those features if you don't want them.

For learning more about the algorithms and how to implement them yourself you can check this out.

Additionally this is a nice resource for showing how to detect intersections between various shapes. Which plays an important role in collision detection.

theoretically, you could store the position of the objects you want to detect collision with in an array.

then just have a simple Boolean(or even void if the game is simple enough) to detect whether a collision has taken place between the object your checking and your sprite/other object that could be doing the colliding.